A Low Fat Diet Decreases High Density Lipoprotein (HDL) Cholesterol Levels By Decreasing HDL Apolipoprotein Transport Rates

This study examined why low-fat diets, which are generally considered heart-healthy, tend to lower HDL cholesterol - often called "good cholesterol." Researchers studied 13 people and measured what happened to their HDL levels when they switched from a high-fat diet to a low-fat, low-cholesterol diet. They also tracked the body's production and breakdown of key HDL proteins to understand the underlying mechanism.

The results showed that HDL cholesterol dropped significantly (by 29%) when participants switched to the low-fat diet. The researchers discovered this happened primarily because the body produced fewer HDL particles, rather than breaking them down faster. Specifically, the production rate of apolipoprotein A-I - a key protein that forms the backbone of HDL particles - decreased by 14%. This reduced production was the main driver of lower HDL levels.

Importantly, the study found that diet-induced changes in HDL levels work differently than natural variations between individuals. While lower HDL production explained why low-fat diets reduce HDL levels, differences in HDL breakdown rates better explained why some people naturally have higher or lower HDL than others on the same diet.

This research suggests that the HDL reduction caused by heart-healthy low-fat diets may not carry the same health risks as naturally low HDL levels. In clinical practice, this means patients shouldn't be overly concerned if their HDL drops when adopting a low-fat diet, as this decrease likely represents a different biological process than having naturally low HDL cholesterol.